<template>
  <view>
    <!-- 搜索条 -->
    <view class="search-box">
      <my-search-bar placeholder="搜索一下" />
    </view>
    <view class="scroll-view-container">
      <!-- 左边的scroll-view -->
      <scroll-view
        class="left-scroll-view"
        scroll-y
        :style="{ height: h + 'px' }"
      >
        <view
          :class="[
            'left-scroll-view-item',
            index === activeIndex ? 'active' : ''
          ]"
          v-for="(item, index) in categories"
          :key="item.cat_id"
          @click="toggle(index)"
        >
          {{ item.cat_name }}
        </view>
      </scroll-view>
      <!-- 右边的scroll-view -->
      <scroll-view
        class="right-scroll-view"
        scroll-y
        :style="{ height: h + 'px' }"
        :scroll-top="scrollTop"
      >
        <view v-for="item in level2List" :key="item.cat_id">
          <!-- 二级标题 -->
          <view class="cate-lv2-title">/ {{ item.cat_name }} /</view>
          <!-- 三级分类 -->
          <view class="cate-lv3-list">
            <view
              class="cate-lv3-item"
              v-for="subitem in item.children"
              :key="subitem.cat_id"
              @click="goToGoodsList(subitem.cat_id)"
            >
              <image :src="subitem.cat_icon" />
              <text>{{ subitem.cat_name }}</text>
            </view>
          </view>
        </view>
      </scroll-view>
    </view>
  </view>
</template>

<script>
export default {
  data () {
    return {
      categories: [],
      activeIndex: 0, // 激活的索引
      h: 0,
      scrollTop: 0
    }
  },
  onLoad () {
    this.getCategoriesData()

    const { windowHeight } = uni.getSystemInfoSync()
    this.h = windowHeight - 50
  },
  computed: {
    level2List () {
      if (this.categories.length > 0) {
        return this.categories[this.activeIndex].children
      } else {
        return []
      }
    }
  },
  methods: {
    async getCategoriesData () {
      const res = await uni.$request({
        url: 'categories'
      })

      if (res.meta.status === 200) {
        this.categories = res.message
      }
    },
    toggle (index) {
      this.activeIndex = index
      this.scrollTop = this.scrollTop === 0 ? 1 : 0
    },
    goToGoodsList (cid) {
      uni.navigateTo({ url: '/subpkg/goods-list/index?cid=' + cid })
    }
  }
}
</script>

<style lang="scss" scoped>
.search-box {
  // 设置定位效果为“吸顶”
  position: sticky;
  // 吸顶的“位置”
  top: 0;
  // 提高层级，防止被轮播图覆盖
  z-index: 999;
}
.scroll-view-container {
  display: flex;

  .left-scroll-view {
    width: 240rpx;

    .left-scroll-view-item {
      line-height: 60px;
      background-color: #f7f7f7;
      text-align: center;
      font-size: 12px;

      // 激活项的样式
      &.active {
        background-color: #ffffff;
        position: relative;

        // 渲染激活项左侧的红色指示边线
        &::before {
          content: ' ';
          display: block;
          width: 3px;
          height: 30px;
          background-color: #c00000;
          position: absolute;
          left: 0;
          top: 50%;
          transform: translateY(-50%);
        }
      }
    }
  }

  .right-scroll-view {
    .cate-lv2-title {
      font-size: 12px;
      font-weight: bold;
      text-align: center;
      padding: 15px 0;
    }
    .cate-lv3-list {
      display: flex;
      flex-wrap: wrap;

      .cate-lv3-item {
        width: 33.33%;
        margin-bottom: 10px;
        display: flex;
        flex-direction: column;
        align-items: center;

        image {
          width: 60px;
          height: 60px;
        }

        text {
          font-size: 12px;
        }
      }
    }
  }
}
</style>
